Sound recording and reproducing apparatus



Sept. 4, 1928. 1,683,451

L. DE FOREST SOUND RECORDING AND REPRODUCING APPARATUS Filed Dec. 19, 1925 III i555:

A BY $555;

has ATTORNEYS. v

Patented Sept. 4,1928.

UNITED STAT/ES PATENT OFFICE.

m a: 10mm, or raw ronx, 11.2., nssmnon'ro 1m roassr rnonorrnx conrona- 21F, 01' NEW YORK,

INK-1., A. CORPORATION OF DELAWARE.

som RECORDING PRODUCING. APPQRATUS.

Application filed December 19, 1925. Serial No. 78,471.

eneral to appaiotographically, the recorded It is one of the purposes of this invention 1 to providemeans whereby the thickness of the light band impinging pon the sensitized film may be readily controlled without distorting the sound waves to be recorded,

This invention resides substantially 1n the 1 combination, construction, arrangement and relative location of parts as will be more fully described hereinafter. a

Referring to the drawings, 'n which the same reference numerals will be used throughout the several viewsto 1nd1catethe same or similar parts, i

Fig. 1 represents a side elevational vlew partly. in section, of the apparatus of my mvention. I

Fig. 2 represents a detail.

,Fig. 3 is a plan view of the members used to form the very fine slit.

\ Fig. is a side elevatlonal-view,

. section, of my novel slit forming mem ers used in connection with sound reproduc ng devices. a

In the phonofilm art it has been rather d1 fficult to produce a sound-influenced, light in the proper form. In ordthat sound. re

i 86 cording and reproducing devices may. record and reproduce sound wavesaccurately, it is necessary that the light impinglng upon the sensitized film be in the form of a very fine thin line; and many attempts have been made i to produce apparatus which will cause the light to take this form. By my device, I am a thin beamof light of any- I able to produce desired thickness. I

In Fig. 1, 1 represents a photion or other 46 light producing device which pro ects from it a ht band 6. The terminals 3 and 4, are inten ed to be connected in the circuit of the sound reproducin apparatus in the well known manner. e light band 6 impinges upon three opaque members 7, 8 and 9, lying in separate parallel planes the member 9,

' having one edge opposed to the edges of the other members?- and 8 s'othat in viewing them from the side as in Fig. 3, they form 5 a very narrow slit 2. The member 9 is adpartl illelement 29, projects a steady ju'stable in its position relative to the other two members throughthe agency of a set 1 screw 10 having a conical end. It will thus be seen that the relatively wide band of light 6 as it impin es upon the slit "forming members is out 0 so as to form a very thm band of light 12, appearing as a fine line in crosssection. This band of light will vary in intensity by and in accordance with the variations in the circuits connected to the terminals, 3 and 4, which are in turn produced by and in accordance with variations in the .sound waves-impinging upon the microphone or sound recording device. This light, varying' in intensity, impinges upon a sensitive film 11 where it is permanently recorded in a well known manner. By mounting the opaque members 7, 8 and 9, in thin parallel planes, there is -no line of li ht, due to the diffraction and multiple re action of the beam as it passes through the plates. If the plates should be placed in the same plane with the edges'directly opposing each other, practically all of the light would be absorbed in the space between them through difiraction and multiple reflection but by my arrangement this difliculty is eliminated. By this arrangement, I am able to obtain on the surface of the photographic filmjll an=ex-' ceedingly narrow and sharply defined plane beam of light 12 with greater efliciency than when the beam of light is passed through any conventional type of slit. At the same time, the light limiting devices 7 8 and 9 may be placeda suitable distance away from the film 11 as it travels at right angles to the light, thus eliminating any possible abrasion of the film surface. I

In Fig. 4 I have shown a similar arran e ment '21 which may be of a relatively large horizontal filament or other light PIOgIiGlIiIg eam o ig t through the travelling film 11 on whichthe' sounds to be reproduced are recorded The quantity of light passing throu h the sound record varies dependingupon tfi the-record and the lightwhich is transmitter. through the film is cut ofi as inFig. 1 by means of the lates 7, 8 and 9, so as to be confined to a re atively plane beam of light '16. This beam of light enters an opaque, box-like i structure22, and impinging upon a'difiusing e density of I lens. 23, spreads out over a light sensitive cell 25. .The terminals 26 and 27 of the light sensitive cell are connected in the usual and well known manner to sound amplified and 4, the dotted lines 11", 11

reproducing devices to convert the electric currents into sound waves. As shown in Fig.

represent other positions which the film 11 may assume, without materially impairing the results of the reproduction, with respect to the members 7, 8 and 9, while confining'the light transmitted to the sensitive cells to a thin plane band and cutting off any extraneous and undesirable rays from influencing the light cell.

. I am, of course, tions in details of construction and arrangement ofthe arts of my invention may be made by one sfiilled in the artwithout departing from the spirit and scope of my invention, and I do not, therefore, desire to be limited to the specificembodiments shown and described by me but rather to the limits defined by the, appended claims.

Having now described my invention, what I seek to securebyUnited States Letters Patent is j 1. In a device for cording and reproducing sound waves, a source of illumination, and means comprising three straight edged opaque bodies 1ying in separate parallel planes to permit an extremely thinv plane of light through the edges of two of said members lying in the same Iplane. I

2. n a device for photographically recording and reproducing sound waves, a source of illumination and means comprising a. plurality of at-least three opposed plane surfaces at least one of which is adjustable with respect to the others to pass light in a thin line the edges of the bers lying in the same plane.

aware that many modificaphotographically reother of said, mem- 19 5 3. In a. device for photo raphically record ing and reproducing soun waves, a source of illumination, and means comprising a plurality of opaque bodies lying in separate planes with opposed edges to pass light in a thin plane.

4. In a sound reproducing andrecording device, a source of illumination, means com-- prising a plurality of at least three relatively Wide opaque bodies disposed with-thin edges roducing and recording beam of light passed, and means for record-- ing variations in intensity of said source of light.

6. In a sound reproducing and recording device, a source of illuminat1on,-means comprising three opaque plane members two of which lie in separate parallel planes on one side of the center line of the light source, and a third member on the opposite side in a plane between the other two, said third member being adjustable with respect to the other two, to vary the thickness of the beam of light passed, means for recording variations in mof hght and'means for tensity of said source diflusing the said thin beam of light.

In testimony whereof I have hereunto set my hand onthis 10th day of December, A. D.,

LEE on FOREST.

a source of illumination, means com- 

